1. Field of Invention
The present invention relates to an active roll rod for a vehicle, and more particularly, to an active roll rod for a vehicle which has been invented to more efficiently suppress vibration, which is transmitted to a vehicle body, depending on a driving state of a vehicle by embedding a damper unit (which is configured to be able to absorb vibration within an overall frequency region by adjusting a frequency of a current), which serves as an active damper, in a fastening unit that is mounted to a sub-frame.
2. Description of Related Art
In passenger vehicles, a monocoque body, which is light in weight and has excellent productivity, is mainly used instead of a frame body. The monocoque body is a structure in which a separate frame is eliminated, and a power train, which is configured by coupling an engine and a transmission, is directly mounted in an engine room of a vehicle body. Therefore, in the case of the monocoque body, the vehicle body itself serves as a frame, and a suspension system and chassis components are mounted thereto, respectively, but a sub-frame is mounted below the vehicle in order to prevent vibration of the power train from being directly transmitted to the vehicle body, and disperse impact at the time of a vehicle collision.
Meanwhile, a four-point mounting manner and a three-point mounting manner are widely adopted depending on a size and disposition of the power train. As a sub-frame that is used in the three-point mounting manner among various mounting manners, an “I” shaped (or an “H” shaped) sub-frame, which is called a dog bone type (the dog bone type is called a roll rod type), is used, a suspension device, a steering device, and the like are coupled to the sub-frame, and the sub-frame is connected to a lower portion of the power train through a roll rod.
That is, as illustrated in FIGS. 1A and 1B, an engine mount 8a and a transmission mount 9a are mounted at both sides of the engine room of the vehicle body, respectively, so as to support loads of an engine 8 and a transmission 9, respectively, and a roll rod 1 is mounted to a sub-frame 7 that is attached to a lower portion, and connected to the transmission 9 so as to control displacement of a power train and attenuate vibration.
Referring to FIG. 1C, in the case of the roll rod 1 in the related art, a fastening unit 4 is mounted between a rod portion 2 and an end plate 6, and insulators 5a and 5b made of synthetic rubber are fitted at a front side (at a left side in FIG. 1C) and a rear side of the fastening unit 4, respectively, so as to support an operation of the roll rod 1 and attenuate vibration.
The rod portion 2 includes a main body portion 2a which is connected to the power train (more particularly, a bracket formed on a lower portion of the transmission) through a bushing 2c mounted to a front end of the rod portion 2, and an inner pipe 2b which is extended from the main body portion 2a. Further, the front insulator 5a, the fastening unit 4, the rear insulator 5b, and the end plate 6 are sequentially disposed and mounted on the inner pipe 2b, and the end plate 6 is fastened to the inner pipe 2b by a fixing bolt 6a. A partition wall portion 4a is formed on an inner circumferential surface of the fastening unit 4 so as to partition the front insulator 5a and the rear insulator 5b, and a flange is formed on an outer circumferential surface of the fastening unit 4, and fastened to the sub-frame by bolting.
In the case of the roll rod 1 having the aforementioned structure, as the rod portion 2 and the end plate 6 are operated together depending on a driving state of a vehicle, the front and rear insulators 5a and 5b are elastically deformed and restored repeatedly to support loads and attenuate vibration. That is, when the vehicle is moved forward, the rear insulator 5b is compressed depending on the displacement of the power train due to inertia so as to support an operation of the power train and perform a damping function, and when the vehicle is moved rearward or decelerated, the front insulator 5a is compressed so as to support an operation of the power train and perform a damping function.
Meanwhile, the recent trend is that an improvement on NVH (noise, vibration, and harshness) performance is required for developing a vehicle, and a cylinder deactivation (CDA) engine (variable cylinder engine) is applied. Accordingly, in order to improve efficiency in attenuating vibration in accordance with a driving state of a vehicle, needs for an active mount having a function of absorbing vibration are increased.
Nom Amongst others, in the case of a front-engine-front-drive (FF) vehicle having the three-point mounting manner, characteristics of vibration, which is transmitted from the power train to the vehicle body, may be determined depending on characteristics of the roll rod. More particularly, in the case of the engine mount 8a or the transmission mount 9a that is configured in a block shape and seated on the vehicle body, the active damper is embedded therein or a separate damper is additionally mounted in the vicinity thereof such that vibration generated in the engine may be more efficiently attenuated, but in the case of the roll rod, the steering device, the suspension device, and the like are seated on the sub-frame, which causes a space to become small, and as a result, there is a problem in that it is difficult to additionally mount the damper. In addition, there occurs a difference in displacement between the roll rod and the vehicle body by an operation of the power train due to the generation of vibration of a vehicle even though a space for additionally mounting the damper in the vicinity of the roll rod is provided in the sub-frame, and as a result, there is a problem in that interference due to the aforementioned configuration needs to be avoided.
In the case of the roll rod, it is very difficult to configure a hydraulic structure in which a hydraulic fluid is sealed as a working fluid, and as a result, there is a problem in that a size of the roll rod is increased when the damper is added because the size of the roll rod becomes very large even if the hydraulic structure is applied.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.